Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems, to the Internet, and to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
Direct or indirect communications may experience be received via multiple pathways. Multiple pathways often result in the deflection of a wireless communications signals off obstacles that can cause interference during reception. Multipath fading occurs when a wireless communications signal is received by an antenna and later the same signal is received again, reflected from an obstacle. This can result from both retransmission and different transmission paths. Under certain conditions, two or more of the signals can interfere with each other and create “fading” (a loss of signal) in the communications link. Fading may occur when signals are retransmitted or received by multiple antennas. Thus, multipath fading may be observed within both wireless and wire-line communications. As the amount of data contained within wireless and wire-line communications increase and the power of the transmitted signal is reduced, the techniques chosen to combat the multipath fading can vary.
Previously, least mean square (LMS) algorithms have been employed to avoid matrix inversion when trying to find the optimum solution to mitigate inter-symbol interference (ISI) or inter-chip interference (ICI). On CDMA downlink, there is strong ICI due to multipaths. To date, adaptive LMS algorithms have been applied to reduce ICI without multipath channel matrix inversion. However, this method produces a biased signal which is not desirable.
Further limitations and disadvantages of conventional and traditional matrix inversion processes or processes used to avoid matrix inversion will become apparent to one of ordinary skill in the art through comparison with the present invention described herein.